Adjustable antenna coil
An antenna coil formed on a substrate surface of an insulating substrate has conductor lines forming four sides of a basic loop shape. Furthermore, the antenna coil has corner lines at a corner portion of the loop. For example, by forming trimming lines on the inner side of one of the corner lines, it becomes possible to adjust the resonant frequency in various ways without considerably disturbing the shape of distribution of magnetic flux density generated by the antenna coil as a whole.
1. An adjustable antenna coil comprising:
first and third conductor lines forming a first pair, extending in a first direction along a predetermined substrate surface and formed with a gap therebetween;
second and fourth conductor lines forming a second pair, extending along the substrate surface in a direction crossing the first and third conductor lines and formed with a gap therebetween;
a plurality of corner portions interconnecting one end of the first conductor line and one end of the second conductor line, the other end of the second conductor line and one end of the third conductor line, and the other end of the third conductor line and one end of the fourth conductor line, thereby forming a conduction path having a loop shape with at least four sides; and
a trimming line formed on an inner side of the conduction path along one of the plurality of corner portions so as to interconnect two sides adjacent via the one corner portion on the conduction path,
wherein the trimming line is formed outside an imaginary rectangle formed by connecting midpoints of individual sides of the conduction path on the substrate surface.
2. The adjustable antenna coil according to claim 1 , wherein the trimming line is formed linearly so as to interconnect the two adjacent sides with one side.
3. The adjustable antenna coil according to claim 1 , wherein the trimming line has a curved shape that is convex toward an outer side of the conduction path.
4. The adjustable antenna coil according to claim 1 , wherein a plurality of trimming lines are provided along the plurality of corner portions.
5. The adjustable antenna coil according to claim 1 , wherein a plurality of trimming lines are provided on the inner side of the conduction path along the one corner portion.
6. An adjustable antenna coil comprising:
first and third conductor lines forming a first pair, extending in a first direction along a predetermined substrate surface and formed with a gap therebetween;
second and fourth conductor lines forming a second pair, extending along the substrate surface in a direction crossing the first and third conductor lines and formed with a gap therebetween;
a plurality of corner portions interconnecting one end of the first conductor line and one end of the second conductor line, the other end of the second conductor line and one end of the third conductor line, and the other end of the third conductor line and one end of the fourth conductor line, thereby forming a conduction path having a loop shape with at least four sides; and
a trimming line formed on an inner side of the conduction path along one of the plurality of corner portions so as to interconnect two sides adjacent via the one corner portion on the conduction path,
wherein the trimming line is formed outside an imaginary ellipse inscribed within the first to fourth conductor lines on the substrate surface.
7. The adjustable antenna coil according to claim 6 , wherein the trimming line is formed linearly so as to interconnect the two adjacent sides with one side.
8. The adjustable antenna coil according to claim 6 , wherein the trimming line has a curved shape that is convex toward an outer side of the conduction path.
9. The adjustable antenna coil according to claim 6 , wherein a plurality of trimming lines are provided along the plurality of corner portions.
10. The adjustable antenna coil according to claim 6 , wherein a plurality of trimming lines are provided on the inner side of the conduction path along the one corner portion.